The present invention relates to an angle measuring device and in particular a device which is useful as a navigation aid.
There is a need in navigation for a device capable measuring of relative bearings to navigation aids or other appropriate targets with respect to the center line of a ship or other free moving vessel. Devices known as a Pelorus, an Alidade or a synchronous Alidade are well known instruments for this purpose as is known by those skilled in the art of navigation.
The principal difficulty encountered in using a conventional Pelorus is maintaining or fixing an accurate sight on a target during rough water conditions. For this reason, the Alidade and synchronous Alidade were developed, they provide gyro stability to the instrument to improve maintaining the sight. These improvements however do not totally eliminate the very human difficulty of operation when the ship is pitching or rolling and further, in the absence of a gyro repeater to provide the ships heading when taking a sight, deriving true bearing information from the Pelorus relative bearing information is extremely difficult requiring considerable cooperation between the Pelorus operator and the helmsman.